This invention relates to an improvement in an induction device equipped with a vibration suppressor.
An induction device such as a transformer, for example, generates vibration due to magnetic strain of silicon steel sheets forming the iron core and due to electromagnetic force resulting from leakage flux and emits vibration noise from the outer circumference of its tank. To suppress the generated vibration, there have been employed such methods as reducing the magnetic flux density of the iron core, disposing an electromagnetic shield on the tank to reduce the leakage flux, and applying a reinforcing material to the outer circumferential wall of the tank. However, none of these methods has provided really satisfactory vibration suppression effects.
Accordingly, there has been proposed an induction device in which a vibration suppressor is disposed outside the outer wall of the tank so as to absorb the outwardly emitted vibration noise. Such a device is disclosed in Japanese Utility Model Publication No. 9132/1961 published on Apr. 22, 1961. In the device disclosed in this prior art reference, a pin is fixed perpendicularly to the surface of the outer circumference of the exterior tank wall and the center of a disc-like vibration plate is fixed to this pin. The sound wave generated by the vibration plate in this device has a 180.degree. phase difference from the sound wave generated by the exterior tank wall. The vibration noise is reduced when both sound waves interfere with each other.
However, the effect of preventing the noise is not satisfactory because the vibration of the vibration plate itself and the emission efficiency of the noise are great. In addition, since the vibration plate has a disc-like form, it is not free from the problem of a space requirement.